ioo TREES GROWING NEAR WATER. 



But more interesting than all else about the tree are the so- 

 called cypress knees, a feature that has baffled the theories 

 and explanations of many. Dr. Charles Mohr, who has studied 

 the. subject most profoundly and is an authority on the form- 

 ation and usefulness of these knees, has been most kind in con- 

 tributing the following account of them to " A Guide to the 

 Trees." In his letter he says : " The following information has 

 been taken as concisely as possible from the statements made in 

 the manuscript of my monograph on Taxodium distichum 

 and transmitted to the Forestry division of the United States 

 department of Agriculture. 



" The pyramidal or conical excrescences of the roots of the 

 cypress known as cypress knees and which form such a 

 striking peculiarity of the trees are always produced under 

 water, or in a constantly water-soaked soil. They are pro- 

 duced often in great number within a radius of from twenty- 

 five to forty feet or more from the trunk, varying from two to 

 six feet and more in height, and always rise above the water. 

 They are simple or with several tumid divisions and normally 

 bare of leaf-bearing sprouts. In the trees approaching their 

 fuller growth they are most frequently hollow, perfectly smooth 

 on the inside of the shell, with its wood compact and firm. 



" The opinion about the uses these knees serve in the house- 

 hold of the tree is divided, and their import to its life is not 

 yet perfectly understood. On one side, it is contended that 

 their purpose is purely mechanical, to serve the tree as an 

 additional means for the support of the enormous weight of 

 the tree in the loose ground, and to increase its resistance to 

 the strain to which it is subjected under the pressure of heavy 

 winds. On a close study of the root system below ordinary 

 water mark, accidentally laid bare, the conclusion can scarcely 

 be avoided that the function of the knees is chiefly mechanical. 

 As an acute observer states, ' to strengthen the roots that the 

 tree may anchor itself safely in a yielding soil, acting as 

 trusses to increase their capacity for holding the tree firmly to 



